Marine Holding Tank

The present invention relates as indicated to a marine holding tank and, more particularly, to a holding tank that converts the excrement and water received from a toilet into vapor and ash components.

Toilets are frequently situated in temporary buildings and moving vehicles for the convenience of employees or passengers, and a connection to a sanitary sewer system may well be monetarily impractical or physically impossible. Accordingly, treatment facilities must be provided with such toilets to enable the sewage to be hygienically stored and/or removed. Reference may be had to the Simpson et al. U.S. Pat. No. 2,678,450 which discloses a sewage reception and treatment tank.

Specifically, such patent teaches the separation of excrement and water by centrifugal force developed in a rotating receiving basket, with the excrement being incinerated within the basket and the water being vaporized outside said basket. This arrangement has certain disadvantages such as the possibility of incomplete separation resulting in some of the excrement being incinerated outside the basket, thereby to preclude complete removal of the dried residue.

Accordingly, it is the principal object of the present invention to provide a holding tank in which the excrement and water of the sewage charge are uniformly treated for reduction to vapor and ashes. This reduction of the charge permits the treated residue to be hygienically stored for a period of time and subsequently to be efficiently removed.

It is a further object of the present invention to provide a holding tank in which excrement and water are mixed into a liquid-solid mixture and such mixture is heated to convert the same to gas and ashes. The mixing and heating of the liquid-solid mixture simultaneously occur in a receiving pan, the mixture being effected by a rotating impeller positioned in said pan with the heating being accomplished by an electric heating means therebelow.

It is yet another object of the present invention to provide electric heating means for the holding tank of the invention selectively having either low or high heating capacity with automatic shut off when the temperature in the holding tank has reached a preselected point. Such temperature is selected to be high enough to evaporate the liquid in the charge and to incinerate the solids of such charge.

It is still another object of the invention to provide a control circuit operative upon manual actuation to complete and hold in the closed condition the heater energizing circuit irrespective of A.C. power interruptions until a preselected temperature has been reached or the control circuit has been manually turned off. This feature of the invention is very important since 115V power from a generator or from a marina source is not always dependable and may be interrupted so that the operating cycle may be discontinued. In such a case, the present invention maintains the energizing circuit in a closed condition for completion of the treatment cycle immediately upon resumption of 115V power.

It is still a further object of the present invention to provide a control circuit for the heater energizing circuit that may be manually actuated or deactuated for operating or deenergizing one or both of the heater elements, respectively, and that is automatically deactuated when the temperature in the holding tank reaches a preselected temperature.

Other objects and advantages of the present invention will become apparent as the following description proceeds.

To the accomplishment of the foregoing and related ends the invention, then, comprises the features hereinafter fully described and particularly pointed out in the claims, the following description and the annexed drawing setting forth in detail a certain illustrative embodiment of the invention, this being indicative, however, of but one of the various ways in which the principle of the invention may be employed.

In said annexed drawing:

FIG. 1 is a partially broken away, schematic perspective environmentally showing the holding tank of the present invention;

FIG. 2 is a vertical cross-section of the holding tank taken substantially along line 2--2 of FIG. 1; and

FIG. 3 is a schematic showing the electrical circuits of the present invention.

Referring now in more detail to the drawing and initially to FIG. 1, the holding tank 10 is mounted in a compartment 11 subjacent the floor or deck 12. A toilet 13 is positioned on the floor 12 and is in fluid communication with the holding tank 10 through inlet conduit 14. Exhaust line 15 runs from the holding tank to the outside wall 16 of the structure within which the holding tank is employed. The invention shown preferably is used in a boat or ship with wall 16 representing the hull thereof, but it will be appreciated that the holding tank could be employed with equal facility in temporary buildings and other vehicles.

Referring now to FIG. 2, the holding tank 10 includes a housing 20 having base plate 21, cylindrical outer shell 22, and annular top wall 23. Base plate 21 extends radially outwardly of cylindrical shell 22 to form flange 25, which is provided with apertures 26 through which suitable fastening means may be passed to secure the holding tank to compartment 11 as shown in FIG. 1. The cylindrical outer shell 22 is provided with access aperture 27 and cover plate 28, pivotal movement of the latter providing easy entry into the housing for maintenance or the like.

At least two feet 30 are provided that extend vertically upwardly from base plate 21 and support horizontally positioned retaining plate 31. A holder indicated generally at 34 comprises a horizontal section 35 and a vertical section 36, with the latter being connected at its lower end to horizontal retaining plate 31 thereby partially to support horizontal section 35 above such plate. The horizontal section of the holder is supported at its other end by a transversely positioned L-shape bracket 37.

The horizontal section 35 of the holder supports two spirally arranged heating elements 38 and 39 thereabove, the respective terminals 40 and 41 of which are connected to separate sources of 115 volt A.C. current as indicated at 42 and 43, respectively. The flow of current to the heating elements is automatically controlled by thermostat 44 both to limit the maximum temperature in the incinerator to a constant value, for example 270.degree. F., and to deenergize the element or elements when boiling and incineration of the solution have been completed. The operation of the electrical circuits and respective elements thereof is discussed in more detail below in context with FIG. 3.

A slightly tapered, stainless steel pan or receiving basket 45 is inserted into the housing 20 through the opening in annular top wall 23, with the bottom wall 46 of the pan resting upon heating coils 38 and 39. The top of the pan side wall is provided with an outwardly turned lip 47 which is welded to pan ring 48. A circular cover plate 49 is connected to pan ring 48 by suitable peripheral fastening means 50, with the ring and cover plate being secured to the housing by fastening means 52 to preclude the pan from rotating.

The cover plate 49 is provided with an intake aperture 53 above which an adapter 54 with aligned and threaded bore 55 is disposed. The male end of a 90.degree. elbow 56 is threaded into bore 55, and the female end of such elbow receives inlet conduit 14 from toilet 13.

An exhaust port (not shown) is provided in the periphery of cover plate 49 at a position approximately 90.degree. from inlet aperture 53, as best shown in FIG. 1. The exhaust aperture is associated with an adapter 58 and elbow 59 similar to those hereinabove described, with the exhaust conduit 15 being connected to elbow 59 and extending outwardly to partition 16.

The cover plate 49 is additionally provided with a centrally located aperture 65 through which rotatable shaft 66 is suspended. The bottom end of the shaft is fitted with a mixing blade 67 which is positioned slightly above bottom 46 of pan 45. At its other end, shaft 66 is coupled to drive shaft 67 of motor 68 by adapter 69. The motor 68 is positioned on holder 70 which surrounds and is connected to bearing retainer 71. Two sets of annular ball bearings 72 are located between bearing retainer 71 and shaft 66 and are maintained in the position shown by annular spacer 73. The bearing retainer 71 is secured to washer 75 by fastening means 76, the washer being welded to cover 49 and being provided with an oil seal 77 in the bore thereof to seal cover 49 to shaft 66.

Referring now to FIG. 3, the control circuit indicated generally at 80 and the heater energizing circuit indicated generally at 81 for the marine holding tank of the present invention are schematically depicted.

The control circuit 80 includes in series a normally closed switch 83 of thermostat 44, a normally closed "off" switch 84, a normally open start switch 85, and a relay circuit generally indicated at 86 connected in parallel to an indicator light 87, all of such elements being coupled across a 12 volt battery source. The thermostat switch 83 is selected to open when a predetermined temperature is attained inside the holding tank 20. It has been found that a temperature of 270.degree. is sufficiently high to insure complete evaporation of the liquid in the charge and complete incineration of the solids in such charge.

The relay circuit 86 includes a switch 87 having finger 87a which is movable respectively between contacts 88 and 89. When switch finger 87a engages contact 88, relay 91 is connected in series with switches 83, 84 and 85. When the coil of relay 91 is energized, normally open contacts 91a of such relay are closed, the contacts 91a being connected across start switch 85. When switch finger 87a engages contact 89, relay 91 is connected in parallel to relay 94 by leads 95 and 96, respectively. Normally open contacts 94a of relay 94 are provided in lead 95, contacts 94a being closed by relay 94 when the coil of the latter is energized.

Referring now to the heater energizing circuit, each of the heating elements 38, 39 is preferably included in a separate circuit having a separate 115 volt A.C. source, with both of such separate circuits being referred to herein as the heater energizing circuit. It will be recognized, of course, that a single A.C. source could be used with the heating elements being selectively arranged in parallel.

With respect to the first separate circuit 100, heating element 38 is connected in series with a second set of normally open contacts 91b of relay 91. The motor 68 for the mixing impeller is connected in parallel with heater element 38. Thus when the coil of relay 91 is energized, contacts 91b will close simultaneously to energize both heating element 38 and motor 68.

Referring now to the second separate circuit 103, heater 39 is connected in series with a second set of contacts 94b of relay 94. When the coil of relay 94 is energized, contacts 94b will be closed to energize heating element 39. The operator of the marine holding tank decides whether to energize only heating element 38 or simultaneously to energize both heating elements 38, 39.

The operation of the marine holding tank is initiated by toilet 13 being flushed to force a charge of excrement and water through conduit 14 into pan 45. The flushing of toilet 13 may be programmed automatically to close start switch 85 or, preferably, start switch 85 may be independently manually actuated. When finger 87a of switch 87 is moved into engagement with contact 88 by the operator and the start switch depressed, only heating element 41 is energized resulting in a relatively "low" heating effect.

More specifically, when the operator chooses the low heating condition, relay 91 is connected in series with switches 83, 84, 85, and 87 and operates to close contacts 91a and 91b. When contacts 91a are closed, the circuit is completed across start switch 85 permitting the same to be released by the operator. Moreover, when contacts 91b are closed by the coil of relay 91, the heater 38 and motor 68 in parallel with one another are simultaneously energized for operation. The energization of motor 68 serves to rotate shaft 66 and impeller 67, thereby thoroughly to mix the excrement and water into a liquid-solid mixture. Simultaneously, heating element 38 heats the pan 45 to the control temperature of 270.degree. F. and vaporizes the liquid portion of the charge while incinerating the solid portion of such charge. Upon reaching the control temperature, thermostat switch 83 opens to discontinue the flow of current to the coil of relay 91, whereby contacts 91b of relay 91 open to deenergize heating element 38 and motor 68. Element 38 and motor 68 may also be manually deenergized at any time by actuating "off" switch 84 which has the same resultant effect of opening relay contacts 91b. During energization of the control circuit in the "low" heating mode, relay 91 will maintain contacts 91b in a closed condition irrespective of A.C. power interruptions that might occur, whereby, when power is resumed, the heating cycle will be completed.

If the operator has selected the "high" position of switch 87, that is with switch finger 87a engaging contact 89, the coil of relay 94 is energized which in turn closes contacts 94a and 94b. When relay contacts 94a are closed, relays 91 and 94 are connected in parallel by leads 95 and 96, with the energization of relay 91 being operative to close contacts 91a and 91b. At such time, both heater circuits are energized resulting in element 38, element 39, and motor 68 simultaneously operating. Even if the 115 volt alternating current power is interrupted, the control circuit will maintain the relay contacts 91b and 94b closed so that upon resumption of power, the operating cycle for the holding tank may be immediately completed. Simultaneous operation of elements 38 and 39 results in more rapid evaporation of the liquid portion of the charge and incineration of the solid portion of the charge than occurs with only element 38 energized.

The "high" heating mode for the holding tank of the present invention is discontinued in the same manner as the "low" mode. More specifically, when the temperature in the holding tank has achieved the control temperature of 270.degree. F., thermostatic switch 83 opens to discontinue current to relays 91 and 94 whereby relay contacts 91b and 94b are opened to discontinue current to heating elements 38 and 39 and motor 68. At any time prior to reaching the control temperature, the control circuit may be opened by actuation of "off" switch 84 similarly resulting in relay contacts 91b and 94b opening to discontinue power to heating elements 38 and 39 and motor 68.

It will be understood, of course, that whenever the control circuit is energized, indicator light 87 will be on. Thus once the control circuit has been actuated, the operator can tell when the heating cycle has been completed by merely observing whether light 87 is off or on.

On completion of the mixing and heating operations by either the "high" or "low" modes, the motor and heating element or elements are deenergized and a dry residue or ash is left in the bottom 46 of pan 45. The residue may be drawn through exhaust conduit 15 by a suction device (not shown) to empty pan 45 for the reception of a subsequent charge. It will be appreciated that the removal procedure does not need to be performed with every operational cycle of the marine holding tank since the dry residue remaining from any one cycle would be insubstantial compared to the volume of the pan.

The cover 49 can easily be removed by loosening the wing nuts on fastening means 50, thereby readily to provide access to pan 45 for cleaning or removal of the dry residue when a suction removal system is not used. Each time cover 49 is removed, a chemical such as copper sulfate should be added to pan 45 to prevent odor during the subsequent treatment process or processes. It will be appreciated that detachment of cover 49 likewise allows motor 68 easily to be maintained or serviced at a location remote from the holding tank.

Thus a marine holding tank is provided that accomplishes complete conversion of an excrement and water charge within a receiving pan, with the converted charge being easily removable by either a suction exhaust conduit or direct extraction from the pan.